Improvements in or relating to alignment apparatus

ABSTRACT

An alignment apparatus for aligning x-ray images with a predetermined set of axes comprises means defining the axes in the form of a support arrangement which supports, at predetermined positions in space, located in at least two predetermined planes, a plurality of elements which are opaque to ex-radiation. An apparatus is also described for aligning an end effector comprising two spaced guide frames each having two parallel guide members with a carriage for movement along each of the guide members, the carriages being inter-connected by cross members, further carriages being mounted on the cross members, the further carriages supporting the end effector for guide means.

BACKGROUND OF THE INVENTION

THE PRESENT INVENTION relates to alignment apparatus. The invention willbe described with reference to alignment apparatus used in the contextof a medical apparatus and, in particular, to a robotically-controlledmedical apparatus, but it is to be understood that the alignmentapparatus of the invention may find different applications.

SUMMARY OF THE INVENTION

Two embodiments of alignment apparatus will be described, one comprisingan apparatus intended to align an X-ray image with predetermined axes,and the other comprising an apparatus to align an end operator with apredetermined direction and a predetermined point in three dimensionalspace.

DESCRIPTION

According to one aspect of this invention there is provided an alignmentapparatus for aligning X-ray images with a predetermined set of axes,comprises means defining the said set of axes, said means comprising asupport arrangement adapted to support, at predetermined positions inspace, located in at least two predetermined planes, a plurality ofelements which are substantially opaque to extradiation.

Preferably the apparatus comprises two components, the components beinglocated in orthogonal planes, each component supporting a plurality ofsaid elements.

Conveniently each component is made of a material which is substantiallytransparent to ex-radiation.

Advantageously each component supports a plurality of said elements in aregular orthogonal array within the component.

Preferably the said elements are present, within each component, as aplurality of rows of evenly spaced elements.

Advantageously within each component there are four rows of elementswhich, when viewed axially, are located at the corners of a square orrectangle, there being at least three elements in each row.

Conveniently the said elements are of different size, different densityrelative to absorption of extradiation and/or of different shape toenable the images of the members to be identified.

Advantageously the first of said planes is horizontal and the second ofsaid planes is vertical, means being provided to take an X-rayphotograph both vertically and horizontally through said elements.

According to another aspect of this invention there is provided anapparatus for aligning an end effector or guide for an end effector witha predetermined point in space at a predetermined orientation, saidapparatus comprising a first guide frame and a second guide frame, thefirst guide frame comprising two substantially vertically extendingguide members, a respective carriage present for sliding movement alongeach of the guide members and a substantially horizontal cross-memberinter-connecting the carriages, there being a further carriage mountedfor horizontal movement on said second horizontal cross-member and asecond frame of similar design spaced from the first frame but being ina plane parallel thereto, the second frame comprising two substantiallyvertical members each provided with a respective carriage for verticalsliding movement on the respective vertical member, the two carriagesbeing inter-connected by a second horizontal cross-member having thereona second carriage for horizontal sliding movement on said secondhorizontal cross-member, the two carriages mounted for horizontalmovement supporting guide means or an end effector.

Preferably drive means are provided to drive the carriages to selectedpositions.

Conveniently the drive means for the carriages are computer controlled.

The computer may be provided with data from an alignment apparatus ofthe type broadly described above.

DESCRIPTION OF THE DRAWINGS

In order that the invention may be more readily understood, and so thatfurther features thereof may be appreciated, the invention will now bedescribed, by way of example, with reference to the accompanyingdrawings in which:

FIG. 1 is a diagrammatic prospective view of one embodiment of analignment apparatus in accordance with the invention, and

FIG. 2 is a diagrammatic perspective view of an alternative form ofalignment apparatus in accordance with the present invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

FIG. 1 illustrates an apparatus for use in aligning an item shown in anX-ray images with predetermined axes, or, in other words, fordetermining the precise position and orientation of an item shown inX-ray images relative to predetermined axes.

It is often very desirable to be able to determine the position of anX-ray image relative to predetermined axes. For example, if a medicalpatient is resting on an operating table and is to be operated on solelyby or with the assistance of a medical robot, it is essential that therobot be provided with precise details as to the position of therelevant part of the patient, on the operating table, and theorientation of that part of the patient, those details being providedwith reference to fixed predetermined axes. The robot may, for example,be required to align a drill, or a guide for a drill, precisely with aparticular part of the patient, with the axes of the drill having apredetermined orientation.

Whilst, when a patient is resting on an operating table, it is possibleto measure with accuracy the position of the exterior parts of thepatient, but often the parts of the patient that are of most importanceare interior parts, such as the bones of the patient.

Whilst it is possible to take X-ray images of a patient, unless veryexpensive C.A.T. (Computer Aided Tomography) apparatus is utilised, suchX-ray images do not immediately provide an accurate indication as to theprecise location of the various parts of the body shown in the X-rayimages. There are various reasons for this, resulting from the fact thatthe X-ray source and the X-ray plate are not, generally speaking,located in a precisely predetermined position, and also arising from thefact that the beam from an X-ray source is generally a "fan" beam, withthe beam diverging from the X-ray tube towards the image-receivingplate. Thus the image received by the plate is not necessarily acompletely accurate image, but is enlarged and possibly distorted and/ordisplaced by the nature of the fan-beam.

Whilst it is possible to take X-ray images from two orthogonaldirections it is often difficult to interpret those images to provide anaccurate indication of the precise spatial position and orientation ofthe parts of the patient shown in the images.

FIG. 1 illustrates alignment apparatus which, when utilised as will nowbe described, reduces the difficulties experienced utilising the priorart techniques.

Referring to FIG. 1 the essential parts of an alignment apparatus areillustrated. The alignment apparatus comprises two alignment components1, 2, which will be described in greater detail, which are held inposition by an appropriate supporting framework 3. The supportingframework may be of any desired design and will thus not be described indetail since the sole function of the supporting framework 3 is tosupport the alignment components 1, 2 in the illustrated position, withthe components 1, 2 preferably being located in a predetermined positionrelative to the upper surface of an operating table, and preferably alsobeing located in a predetermined position relative to a medical robotwhich is to be utilised in performing an operation on a patient restingon the operating table.

The alignment components 1, 2 are each of elongate form and are locatedorthogonally, with the alignment component 1 having a substantiallyhorizontal central axis and the alignment component 2 having asubstantially vertical central axis.

Each alignment component comprises a rectangular block 4 of a materialthat is substantially transparent to X-rays. This material may compriseplastic material, but other materials may be utilised.

Mounted within each block 4 are a plurality of elements such as balls 5made of a material that is opaque to X-rays. The balls may be made ofmetal or some other material that absorbs X-rays. Preferably the balls 5are of different sizes relative to each other or are designed to absorbdifferent quantities of X-rays, or are fabricated to be of differentshapes, so that the images of the balls 5 may be recognised individuallyon an X-ray plate.

In each block 4 there are twelve balls 5. The balls are arranged in fouraxially extending rows 6. The ends of the rows 6, when viewed axially,form a square array. Each row is provided with three balls, the ballsbeing uniformly spaced.

Referring to FIG. 1 it can be seen that the alignment components 1 and 2are located adjacent an area of space 7 which, in use of the illustratedarrangement, in the manner presently being described by way of example,will contain part of a patient. A first X-ray image is taken of thatpart of the patient by directing an X-ray beam downwards in thedirection indicated by the arrow 8, and a second X-ray image is taken bydirecting an X-ray beam horizontally in the direction indicated by thearrow 9.

In each of the resultant X-ray plates there will be images of the balls5 present in both of the alignment components 1 and 2. Since theorientation and spacing of these elements is known, it is possible forappropriate calculating means, such as a computer, to calculate detailsof the divergence of the fan beam and consequently for the calculatingmeans to determine the precise position and precise orientation of theparts of the patient present within the X-ray image, with reference tothe axes defined by the alignment components 1 and 2.

It is envisaged, therefore, that the two X-ray images would be exhibitedon an appropriate computer screen, and using a mouse or other equivalentmeans, a line of action would be marked on the screen. For example, ifthe screen showed a bone and it was necessary to drill a channel oropening into the bone, an appropriate line could be marked on each ofthe X-ray images present on the screen to show the precise position anddirection of the line of action relative to the bone. Using the imagesof the various balls present in the alignment computers 1 and 2, acomputer could then calculate, with reference to the axes effectivelydefined by the alignment components, the precise position andorientation to be occupied by the drill at the commencement of thedrilling operation.

Whilst this embodiment has been described with specific reference toaligning images of part of a patient with predetermined axes, thedescribed apparatus could be used for other purposes.

Reference will now be made to FIG. 2 of the accompanying drawings whichillustrates an alignment apparatus in the form of an apparatus adaptedto align a guide in a predetermined manner.

Whilst apparatus of the type shown in FIG. 2 may have many applications,the apparatus shown in FIG. 2 may be specifically intended for use inguiding a drill to be actuated by a surgeon during an operation on apatient. The drill, in such a situation, will have to enter the patientat a precisely predetermined point and the drill must have a preciselypredetermined orientation relative to the patient. It is envisaged that,from appropriate input data (for example, data from the X-ray techniquedescribed above) a computer will determine the position and thedirection made by the drill. The apparatus illustrated in FIG. 2 formthe operative part of a robot which is controlled by the computer 26 andwhich may be utilised to position the guide so that the drill may becorrectly located.

Whilst it has been proposed previously to utilise robots to positionoperators such as drill, spray-guns and the like, such prior proposedrobots have used multi-articulated arms. Whilst an arm of this type doesenable a drill, spray-gun or the like to be located at any position inspace, with that drill or spray-gun directed in a predetermineddirection, the multi-articulation provides a not inconsiderable degreeof error. In many applications the error is not a problem, but it willbe appreciated that in a situation where a drilling operation is to beperformed on a patient, any error is unacceptable. Thus the apparatus ofFIG. 2 may be used to position a guide with a very low degree of error.

Referring now to FIG. 2 the alignment apparatus there illustratedcomprises a support or base 10. The support or base may have a preciselypredetermined located relative to an operating table, so that whendetails of the position of a patient present on the operating table havebeen analysed, and a specific location and orientation have beendetermined for a drill, a guide forming part of the apparatus may bepositioned to guide the drill to that specific position with thatspecific orientation.

The base 10 supports two guide frames which are spaced apart and locatedin parallel planes. The first guide frame comprises a first verticalmember 11 and a second vertical member 12 at spaced apart positionslocated at the rear of the base 10 as illustrated in FIG. 2. A firstcarriage 13 is provided which is slidable up and down the verticalmember 11, and a second carriage 14 is provided which is slidable up anddown the vertical member 12. A horizontal cross-beam 15 extends betweenthe two carriages 13 and 14. The design of the vertical members 11, 12and the carriages 13, 14 are such that the carriages may only move insynchronism, so that the horizontal cross-beam 15 is always horizontal.

A carriage 16 is provided for horizontal movement along the horizontalcross-beam 15.

The second guide frame is of a similar design, and is in a planeparallel to but spaced from the plane of the first frame. The secondframe comprises two vertical members 17, 18 located at the front of thebase 10 as illustrated in FIG. 2. A carriage 19 is provided for verticalmovement on the vertical member 17 and a carriage 20 is provided forvertical movement on the vertical member 18. A horizontal cross-piece 21extends between the two carriages 19 and 20, and a further carriage 22is provided for horizontal movement on the horizontal cross-piece 1.

Again the design of the vertical member 17, 18 and the carriages 19, 20are such that the carriages may only move in synchronism, so that thehorizontal cross-piece 21 is always maintained in a horizontal position.

A tubular guide element 23 is supported on the carriages 16 and 22 whichare movable along the horizontal cross members 15 and 21.

It is to be appreciated that by locating the carriages 13, 14, 19, 20,16 and 22 at appropriate positions, the guide element 23 may be locatedto have any predetermined orientation and may be located at anypredetermined position within the confines of the frames.

It is to be appreciated that in the described embodiment the variouscarriages will be moved to the desired positions by appropriate drivemechanisms 25 controlled by the computer 26, but in alternativeembodiments of the invention the various horizontal members may beprovided with graduations, and the horizontal cross-bars may be providedwith graduations, and the various carriages may be moved to the desiredpositions by hand.

Whilst, in the described embodiment, the carriages on the horizontalcross-beams simply carry a tubular guide, it is to be appreciated thatthe carriages may, in alternate embodiments of the invention, carry anend effector, such as a drill, a spray-gun or the like.

I claim:
 1. An apparatus for aligning an end effector or guide for anend effector with a predetermined point in space at a predeterminedorientation, said apparatus comprising a first guide frame and a secondguide frame, the first guide frame comprising two substantiallyvertically extending guide members, a respective carriage present forsliding movement along each of the guide members and a substantiallyhorizontal cross-member inter-connecting the carriages, there being afurther carriage mounted for horizontal movement on said horizontalcross-member and a second guide frame of similar design spaced from thefirst guide frame but being in a plane parallel thereto, the secondguide frame comprising two substantially vertical members each providedwith a respective carriage for vertical sliding movement on therespective vertical member, the two carriages being inter-connected by asecond horizontal cross-member having thereon a second carriage forhorizontal sliding movement on said second horizontal cross-member, thetwo carriages mounted for horizontal movement supporting guide means oran end effector.
 2. An apparatus according to claim 1 wherein drivemeans are provided to drive the carriages to selected positions.
 3. Anapparatus according to claim 2 wherein the drive means for the carriagesare computer controlled.
 4. An apparatus according to claim 3 whereinthe computer is provided with data from an alignment apparatus.